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When it goes into closed loop vehicle lopes and engine stalls

Tiny
BOBBIEBRYANT
  • MEMBER
  • 2004 PONTIAC GRAND PRIX
  • 3.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 170,000 MILES
The car starts fine and will run real good and strong. Then it shudders and begins to lope RPM's up and down. Then it shuts off. It will start back up but it doesn't run for ore than about a minute. Performed fuel pressure checks, spark check, injector pulse. I have checked all the basics. Watching the scanner data I can find nothing to cause this problem. All parameters look correct. I was looking at the data and see that as soon as it goes into closed loop is when my problem begins. After I couldn't find anything, I changed the MAF sensor, MAP sensor, and O2 sensors as a guess. I have the scanner data available. I have been doing this a long time and I've not been stumped like this.
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Thursday, June 27th, 2019 AT 4:09 PM

17 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,656 POSTS
No codes correct? These cars had a problem with the ignition module and coil pack. It wont cause codes but it does create the problem you have described. Here is how to do the replacement. Check out the diagrams (below). Please let us know what happens.
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Saturday, June 29th, 2019 AT 7:18 PM
Tiny
BOBBIEBRYANT
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  • 8 POSTS
You are correct. No codes. I swapped the ICM and coil packs with a known good on the shelf, no change. I have included a screenshot of the scanner data. It seems to show that the exhaust gets richer until it shuts off.
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Monday, July 1st, 2019 AT 4:00 AM
Tiny
KEN L
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See the MAF readings showing a possible plugged catalytic converter. To be sure lets use this guide to confirm the issue:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Please run down this guide and report back.

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Monday, July 1st, 2019 AT 11:23 AM
Tiny
BOBBIEBRYANT
  • MEMBER
  • 8 POSTS
Checked the catalytic converter. It looks like it's pretty new. It checks out. I took it off and ran the engine. I had the exact same symptoms (except louder). Ran smooth at first, then began to surge and eventually shut off.
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Thursday, July 18th, 2019 AT 11:49 AM
Tiny
KEN L
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Sounds like the PCM is loosing its program and must be reset to start working again. Fuel pressure okay? If so I would swap out the PCM here is the location

Here is a guide

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Fuel Pressure (Key ON Engine OFF) .................... 380-410 kPa (55-60 psi)

Check out the diagrams (below). Please let us know what happens.

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Friday, July 19th, 2019 AT 4:53 PM
Tiny
BOBBIEBRYANT
  • MEMBER
  • 8 POSTS
Fuel pressure is within spec and never changes even through the surges. The PCM has already been changed. It is new.
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Friday, July 19th, 2019 AT 5:46 PM
Tiny
KEN L
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I am wondering if the oil pressure cut off it coming into play here, does the engine have fresh oil, level good? Can you please shoot a quick video with your phone so we can see what's going on, that would be great. You can upload it here with your response.
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Saturday, July 20th, 2019 AT 10:43 AM
Tiny
BOBBIEBRYANT
  • MEMBER
  • 8 POSTS
https://youtu.be/1kVOZp2grGc

This is the only way I could figure out how to upload the video. I guess the file is too large to add it here.

Also I know that the dash temp gauge isn't working. But the scanner data shows the temperature sensor is working appropriately.
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Tuesday, July 30th, 2019 AT 3:56 PM
Tiny
KEN L
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Good job on the video. it sounds like you have a bearing bearing out on a serpentine belt tensioner. lets remove the belt and restart the engine to see if the noise and running issue goes away. Here is a guide to help you remove the belt. Do not run the engine more than 2 minutes.

https://www.2carpros.com/articles/replace-serpentine-belt

Please run down this guide and report back.
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Wednesday, July 31st, 2019 AT 11:26 AM
Tiny
BOBBIEBRYANT
  • MEMBER
  • 8 POSTS
Sorry for the delay, it has been hectic here. I did this when I first got the vehicle but I went ahead and did it again. It does best I can tell the same thing. But the battery gave out before it died completely. I am going to get a large capacity jump pack I have access to and try it again if needed. It is a new battery.

https://youtu.be/kGJonZAZOy8
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Saturday, August 10th, 2019 AT 8:17 AM
Tiny
KEN L
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Yep, the noise is gone so we need to spin each of the bearing accessories such as the alternator, water pump and belt tensioner to see which one is not turning smoothly.

This video shows how what to look for:

https://youtu.be/gblcSbyGgv4

Please run down this guide and report back telling me which one is having an issue so I can send instructions on how to fix it.

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Saturday, August 10th, 2019 AT 11:44 AM
Tiny
BOBBIEBRYANT
  • MEMBER
  • 8 POSTS
I know the noise is gone. It is the power steering pump. But the engine still lopes and dies. That is not the reason for the runability problem.
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Saturday, August 10th, 2019 AT 1:02 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Okay, when you are reading the data do you see the coolant temperature sensor value? It sounds like it maybe shorting out when warm. Here is the location so you can swap it out. Check out the diagrams (below). Please let us know what happens.
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Monday, August 12th, 2019 AT 10:22 AM
Tiny
BOBBIEBRYANT
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  • 8 POSTS
I can see it on the scanner data and it is steady without any erratic behavior. But I will change it be sure.
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Monday, August 12th, 2019 AT 10:42 AM
Tiny
KEN L
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Good call, let me know.
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Monday, August 12th, 2019 AT 12:04 PM
Tiny
TFRITH
  • MEMBER
  • 3 POSTS
Did you ever resolve the stalling when in closed loop problem? I'm having the same exact issue on a 2000 Toyota Tacoma 2.7L.
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Saturday, August 1st, 2020 AT 9:33 AM
Tiny
KEN L
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I believe he replaced the PCM. Can you please post your new question here, you must be logged in.

https://www.2carpros.com/questions/new

Cheers, Ken
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Saturday, August 1st, 2020 AT 11:38 AM

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